| The online stability assessment technique is developed under the ground of interconnected power system rapid development,power market etc.The purpose is to improve the online master and control stability of power system stability.The dissertation conducts research work on the power system online assessment and decision techique.The main research is focused on the online stability comprehensive assessment method including the analysis of system stability state,automatic identification of weak tranmission sections,online asssessment of stability control strategy and the evaluation of stability level.And the decision method for generator angle stability is also conducted.The stability state anlaysis function is mainly for the analysis of stability state and stability nature in the power system eletromechanic transisent simualtion.In the aspect of stability state analysis,a practical analysis method based on the generator angle,bus voltage etc.is put forward to analyz wheather the system is stable or not.The stability nature analysis is mainly focused on the angle stability and voltage stability.For the angle stability problem,the oscillation center computation method is put forward to analyze the angle problem and the oscillation center section between homological unit group.For the voltage stability problem,the load bus voltage usually keeps long time and is different from that of angle stability,which usually keeps oscillation.The voltage stability judgement method is put forward which is based on the load current-power curve or load bus voltage.If the load current is kept increasing and the power is kept reducing or the load voltage is kept for long time,it may be the voltage stability problem.The weak transmission section identification function includes automatic searching and fast identification.The searching method based on sub-network or station automatic combination is put forward to search two types of tranmission sections,which include sections with only one voltage grade lines and sections with different voltage grade lines.The static limit is selected to assess the weak degree of transmission section,and the multi-port thevenin equivalent method is put forward to estimate the static limit.The indentification method is based on the the network structure change influence on the steady static limit,and the implicit factor of section lines disconnect is mainly considered.The stability control strategy assessment function includes standardization of control strategy,automatic matching of operation data.The standardization process changes different types of control strategy into some data tables with different attributes,which can be easily processed by compute.The control strategy matching finds the valid control measure of given power flow data,which forms the data base of statbility computation.The comprehensive stability assessment is based on large amount of computation results and the the stability state anlaysis results,weak transmission section identification and the stability control stragety assessment.The comprehensive stability assessment function should analyze and find the main informaton related to stability state,evaluate and show the stability state of whole system.The decision of angle stability function mainly considers two types of application including auxiliary adjustment decision and emergency control decision.The basis of this method is the analysis of power network structure.Combining with the offline simulation and analysis experience,the decision method includes four steps including oscillation center identification,adjustable system identificaiton,adjustable device identification and simualtion verification.The study of this dissertation is an in-depth study of the current online stability assessment techique.All the methods have been applied in the north china,east china and central china interconnected power network,and have played a good role. |
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